Optical device and method for modifying the refractive index of an optical material

ABSTRACT

An optical device comprising an optical hydrogel with select regions that have been irradiated with laser light having a pulse energy from 0.01 nJ to 50 nJ and a wavelength from 600 nm to 900 nm. The irradiated regions are characterized by a positive change in refractive index of from 0.01 to 0.06, and exhibit little or no scattering loss. The optical hydrogel is prepared with a hydrophilic monomer.

This patent application is a division of U.S. patent application Ser.No. 15/455,870 filed Mar. 10, 2017, which is a continuation of U.S.patent application Ser. No. 14/564,207 filed Dec. 9, 2014, now U.S. Pat.No. 9,622,912, which is a divisional of U.S. patent application Ser. No.13/686,952 filed Nov. 28, 2012, now U.S. Pat. No. 8,932,352, which is acontinuation of U.S. patent application Ser. No. 12/846,950 filed Jul.30, 2010, now U.S. Pat. No. 8,337,553, which is a divisional applicationof U.S. patent application Ser. No. 11/948,298 filed Nov. 30, 2007, nowU.S. Pat. No. 7,789,910, which is a continuation-in-part of U.S. patentapplication Ser. No. 11/745,746 filed May 8, 2007, which claims thebenefit of U.S. provisional application Ser. No. 60/817,027 filed Jun.28, 2006.

The present invention relates to a method of using a laser to modify therefractive index of an optical device, and the resulting optical device.

BACKGROUND OF THE INVENTION

In general, there are two types of intraocular lenses. One type replacesthe eye's natural lens, usually to replace a cataractous lens. The othertype is used to supplement an existing lens and functions as a permanentcorrective lens. This type of lens (referred to as a phakic IOL) isimplanted in the anterior or posterior chamber to correct refractiveerrors of the eye. In theory, the power for either type of IOL requiredfor enmetropia (i.e., point focus on the retina from light originatingat infinity) can be precisely calculated. The power of the implantedlens is selected based on pre-operative measurements of ocular lengthand corneal curvature to enable the patient to see without or withlittle vision correction. Unfortunately, due to errors in measurement,variable lens positioning or wound healing, most patients undergoingcataract surgery will not enjoy optimal vision without some form ofvision correction following the surgery (Brandser et al., Acta OpthalmolScand 75:162 165 (1997); Oshika et al., J Cataract Refract Surg 24:509514 (1998). Because the power of present IOLs cannot be adjustedpost-implantation, the patient typically must use additional correctivelenses such as eye glasses or contact lenses.

One potential solution to the foregoing problem is a light-adjustableintraocular lens whose refraction properties can be modified followinginsertion of the lens into a human eye. Such a lens is reported in U.S.Pat. No. 6,450,642, hereafter referred to as the Calhoun Patent. Thelight-adjustable lens is said to comprise (i) a first polymer matrix and(ii) a refraction modulating composition (RMC) that is capable ofstimulus-induced polymerization. As stated, when a portion of thedescribed lens is exposed to light of sufficient intensity, the RMCforms a second polymer matrix. The process is said to result in a lightadjusted, power-modified lens.

As described in the Calhoun Patent, the first polymer matrix and the RMCare selected such that the components that comprise the RMC are capableof diffusion within the first polymer matrix. Put another way, a loosefirst polymer matrix will tend to be paired with larger RMC componentsand a tight first polymer matrix will tend to be paired with smaller RMCcomponents. Upon exposure to an appropriate energy source (e.g., heat orlight), the RMC typically forms a second polymer matrix in the exposedregion of the optical element. After exposure, the RMC in the unexposedregion will migrate into the exposed region over time. The amount of RMCmigration into the exposed region is time dependent and may be preciselycontrolled. If enough time is permitted, the RMC components willre-equilibrate and redistribute throughout the lens material (i.e., thefirst polymer matrix, including the exposed region). When the region isre-exposed to the energy source, the RMC that has since migrated intothe region polymerizes to further increase the formation of the secondpolymer matrix. This process (exposure followed by an appropriate timeinterval to allow for diffusion) may be repeated until the exposedregion of the optical element has reached the desired property (e.g.,power, refractive index, or shape). The entire optical element is thenexposed to an energy source to “lock-in” the desired lens property bypolymerizing the remaining RMC in the lens material. Overall, the powerof the lens is changed by a shape change caused by the migrating of theRMC and subsequent polymerization(s).

U.S. Pat. No. 7,105,110 describes a method and instrument to irradiate alight adjustable lens with an appropriate amount of radiation in anappropriate pattern. The method is said to include aligning a source ofthe modifying radiation so as to impinge the radiation onto the lens ina pattern, and controlling the quantity of the impinging radiation. Thequantity of the impinging radiation is controlled by controlling theintensity and duration of the irradiation.

There exists an ongoing need for new materials and processes to improvea patient's vision following cataract surgery. In particular, there is aneed for an IOL material whose refractive power can be modified by achange in the refractive index of the lens material post-operativeimplantation.

SUMMARY OF THE INVENTION

An optical device comprising an optical hydrogel with select regionsthat have been irradiated with laser light having a pulse energy from0.01 nJ to 50 nJ and a wavelength from 600 nm to 900 nm. The irradiatedregions are characterized by a positive change in refractive index offrom 0.01 to 0.06, and exhibit little or no scattering loss. The opticalhydrogel is prepared with a hydrophilic monomer.

A method of changing the index of refraction of an optical hydrogel thatis a component of an optical device implanted in the eye of a patientfor vision correction. The method comprises providing a physician with alaser system to irradiate select regions of the optical hydrogelfollowing implantation of the optical device into the eye of thepatient. The laser system comprises a laser having a pulse energy from0.01 nJ to 50 nJ and a light wavelength from 600 nm to 900 nm. Theirradiated regions are formed by scanning the laser light in an X-Yplane perpendicular to the laser beam, and the irradiated regionscharacterized by a positive change in refractive index of from 0.01 to0.06 and exhibit little or no scattering loss.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following descriptionand in consideration with the accompanying figures. It is to beexpressly understood, however, that each of the figures is provided tofurther illustrate and describe the invention and is not intended tofurther limit the invention claimed.

FIG. 1 is a microscope photograph of a line grating written in anoptical, polymeric material produced by laser irradiation;

FIG. 2 is a microscope photograph of a line grating written above andorthogonal to another line grating in an optical, polymeric materialproduced by laser irradiation;

FIG. 3 is a microscope photograph of an array of cylinders etched in anoptical, polymeric material produced by laser irradiation;

FIG. 4 is a microscope photograph of one array of cylinders (20×20)etched above and slightly offset to another array of cylinders (20×20)in an optical, polymeric material produced by laser irradiation;

FIG. 5 is a schematic representation of a three-dimensional structure inan optical, polymeric material that can be produced by laserirradiation;

FIG. 6 is a schematic representation of creating a convex, plano orconcave structure in an optical, polymeric material to yield a positiveor negative correction;

FIG. 7 is a schematic representation of the laser and optical systemused to write the structures shown in FIGS. 1 to 4;

FIG. 8 shows schematically an arrangement of a sample for modificationby a laser;

FIGS. 9A and 9B show the Raman spectra of the base material and theirradiated regions of balafilcon A;

FIG. 10 shows the Raman spectrum of a region of balafilcon A irradiatedwith relatively high energy, femtosecond laser pulses; and

FIG. 11 shows a radial (micromachined) refractive structure in anacrylic IOL material.

DETAILED DESCRIPTION OF THE INVENTION

If very short laser pulses of sufficient energy are tightly focused onan optical, polymeric material, the high intensity of light at the focuspoint causes a nonlinear absorption of photons (typically multi-photonabsorption) and leads to a change in the refractive index of thematerial at the focus point. Moreover, the region of the material justoutside the focal region is minimally affected by the laser light.Accordingly, select regions of an optical, polymeric material can bemodified with a laser resulting in a change in the refractive index inthese regions.

The invention is directed to a method for modifying the refractive indexof an optical device. The method comprises irradiating select regions ofan optical, polymeric material of the device with a focused, visible ornear-IR laser having a pulse energy from 0.05 nJ to 1000 nJ. Theirradiated regions exhibit no significant differences in the Ramanspectrum with respect to the non-irradiated optical, polymeric material.Also, the irradiated regions exhibit little or no scattering loss, whichmeans that the structures formed in the irradiated regions are notclearly visible under appropriate magnification without contrastenhancement.

The pulse energy of the focused laser used in the method will in-partdepend on the type of optical material that is being irradiated, howmuch of a change in refractive index is desired and the type ofstructures one wants to imprint within the material. The selected pulseenergy will also depend upon the scan rate at which the structures arewritten into the optical material. Typically, greater pulse energieswill be needed for greater scan rates. For example, some materials willcall for a pulse energy from 0.2 nJ to 100 nJ, whereas other opticalmaterials will call for a pulse energy from 0.5 nJ to 10 nJ.

The pulse width must be preserved so that the pulse peak power is strongenough to exceed the nonlinear absorption threshold of the opticalmaterial. However, the glass of the focusing objective(s) significantlyincreases the pulse width due to the positive dispersion of the glass. Acompensation scheme is used to provide a corresponding negativedispersion that can compensate for the positive dispersion introduced bythe focusing objective(s). Accordingly, the term “focused” in thisapplication refers to the focusing of light from a laser within anoptical, polymeric material using a compensation scheme to correct forthe positive dispersion introduced by the focusing objective(s). Thecompensation scheme can include an optical arrangement selected from thegroup consisting of at least two prisms and at least one mirror, atleast two diffraction gratings, a chirped mirror and dispersioncompensating mirrors to compensate for the positive dispersionintroduced by the focus objective.

In one embodiment, the compensation scheme comprises at least one prism,in many cases at least two prisms, and at least one mirror to compensatefor the positive dispersion of the focusing objective. In anotherembodiment, the compensation scheme comprises at least two gratings tocompensate for the positive dispersion of the focusing objective. Anycombination of prisms, gratings and/or mirrors can be used for thecompensation scheme.

The use of the compensation scheme with the focusing objective cangenerate pulses with a pulse energy from 0.01 nJ to 100 nJ, or from 0.01nJ to 50 nJ, and a pulse width of from 4 fs to 200 fs. At times, it canbe advantageous to generate a laser pulse with energies from 0.2 nJ to20 nJ, and a pulse width of from 4 fs to 100 fs. Alternatively, it canbe advantageous to generate a laser pulse with energies from 0.2 nJ to10 nJ and a pulse width of from 5 fs to 50 fs.

The laser will generate light with a wavelength in the range from violetto near-infrared radiation. In various embodiments, the wavelength ofthe laser is in the range from 400 nm to 1500 nm, from 400 nm to 1200 nmor from 600 nm to 900 nm.

In one particular embodiment, the laser is a pumped Ti:sapphire laserwith an average power of 10 mW to 1000 mW. Such a laser system willgenerate light with a wavelength of approximately 800 nm. In anotherembodiment, an amplified fiber laser that can generate light with awavelength from 1000 nm to 1600 nm can be used

The laser will have a peak intensity at focus of greater than 10¹³W/cm². At times, it may be advantageous to provide a laser with a peakintensity at focus of greater than 10¹⁴ W/cm², or greater than 10¹⁵W/cm².

The method of the invention provides an opportunity for an ocularsurgeon to modify the refractive index of an optical device, e.g., anintraocular lens or corneal inlay, after the device has been implantedinto the eye of a patient. The method allows the surgeon to correct anyaberrations as a result of the surgery. The method also allows thesurgeon to adjust the power of the lens or inlay by increasing therefractive index in the irradiated regions. For example, starting from alens of selected power (will vary according to the ocular requirementsof the patient), the surgeon can further adjust the refractiveproperties of the lens to correct a patients vision based upon theindividual needs of the patient. In essence, an intraocular lens wouldessentially function like contact lenses or glasses to individuallycorrect for the refractive error of a patient's eye. Moreover, becausethe implanted lens can be adjusted by increasing the refractive index ofselect regions of the lens, post-operative refractive errors resultingfrom pre-operative measurement errors, variable lens positioning duringimplantation and wound healing (aberrations) can be corrected or finetuned in-situ.

For instance, cataract surgery typically requires that the natural lensof each eye be replaced with an intraocular lens (IOL). Followinginsertion of the IOL the surgeon can correct for aberrations resultingfrom the surgery or correct for slight misplacement of the IOL.Following surgery, and after allowing time for the wound to heal, thepatient would return to the surgeon to have select regions of the IOLirradiated. These irradiated regions would experience a positive changein refractive index, which would correct for the aberrations as well asthe patients needs for vision correction. In some instances, the surgeonwould be able to adjust the IOL in one eye for distance and adjust theIOL in the opposite eye for reading.

Typically, the irradiated portions of the optical material will exhibita positive change in refractive index of about 0.01 or more. In oneembodiment, the refractive index of the region will increase by about0.03 or more. In fact, applicants have measured a positive change inrefractive index in an optical silicone-containing hydrogel of about0.06.

It is to be understood by one of ordinary skill in the art, that themethod of the invention modifies the optical properties of the materialnot by casting an optical material with nonreacted monomer (refractionmodulation composition) followed by laser irradiation to promoteadditional polymerization chemistry as described in the Calhoun Patent,but rather by changing the refractive index of an already completelypolymerized optical material. The term “completely polymerized” whenused to characterize the optical materials used in the method means thatthe optical materials are 95% or more polymerized. One way to measurethe completeness of a polymerized optical material is by near infra-redspectroscopy, which is used to qualitatively determine the vinyl contentof the material. Simple gravimetric weight analysis can also be used.

The irradiated regions of the optical device formed by the method of theinvention can be defined by two- or three-dimensional structures. Thetwo- or three-dimensional structures can comprise an array of discretecylinders. Alternatively, the two- or three-dimensional structures cancomprise a series of lines (a grating) or a combination of an array ofcylinders and a series of lines. Moreover, the two- or three-dimensionalstructures can comprise area or volume filled structures, respectively.These area or volume filled structures are formed by continuouslyscanning the laser over a select region of the polymeric material.

Nanometer-sized structures can also be formed by the zone-plate-arraylithography method describe by R. Menon et al., Proc. SPIE, Vol. 5751,330-339 (May 2005); Materials Today, p. 26 (February 2005).

In one embodiment, the irradiated regions of the optical device aredefined by a series of lines in a two dimensional plane having a widthfrom 0.2 μm to 3 μm, preferably a width from 0.6 μm to 1.5 μm and aheight from 0.4 μm to 8 μm, preferably a height from 1.0 μm to 4 μm(height is measured in the z direction of the material, which isparallel to direction of the laser light). For example, one can generatea line grating comprising a plurality of lines with each line of anydesired length, about 0.8 μm to about 1.5 μm in width and about 2 μm to5 μm in height. The lines can be separated by as little as 1.0 μm (0.5μm spacing), and any number of lines can be incorporated into thematerial. Moreover, the grating can be positioned at any selected depth(z-direction), and any number of line gratings can be generated atvarious depths into the material.

FIG. 1 is a microscope photograph with contrasting background of a linegrating comprising 20 lines written into an optical material. Each lineis about 100 μm in length, about 1 μm in width with a line separation ofabout 5 μm. The lines have a height of about 3 μm and were written intothe material at a distance of about 100 μm from the top surface of thematerial. Similar microscope photographs exhibiting line gratings wereobtained at a distance of about 200 μm and 400 μm from the top surfaceof the material, thereby demonstrating that structures can be writteninto the optical material at any selected depth.

FIG. 2 is a microscopic photograph with contrasting background of oneline grating written above and orthogonal to another line grating. Eachof the gratings has a similar dimensional structure to that describedfor FIG. 1 above. One line grating is positioned about 100 μm into thematerial, and the other line grating is positioned about 110 μm into thematerial for a center-line, grating separation of about 10 μm. Again,each of these line structures has a height (depth) of about 3 μm.

FIG. 3 is a microscopic photograph with contrasting background of anarray of cylinders written into an optical material. Each cylinder isabout 1 μm in diameter with a height of about 3 μm. The cylinders areseparated by about 5 μm. The cylinders were etched into the material ata distance of about 100 μm from the top surface of the material.

FIG. 4 is a microscopic photograph with contrasting background of onearray of cylinders (20×20) written above and slightly offset to anotherarray of cylinders (20×20). Each of the cylinders has a similardimensional structure to that described for FIG. 3 above. One array ispositioned about 100 μm into the material, and the other array ispositioned about 105 μm into the material for a center-line separationof about 5 μm. Each of the cylinders has a height (depth) of about 3 μm.

The area-filled or volume-filled two- or three-dimensional structurescan be formed by continuously scanning the laser over selected regionsof the optical, polymeric material. Refractive-type optical devices canbe micro-machined inside the volume of an optical, polymer material byrepeatedly scanning a tightly focused beam of femtosecond pulses in anarea segment. The area of the segment can be changed correspondinglywith the depth of the scan, so as to produce three-dimensionally shapedlenses with spheric, aspheric, toroidal or cylindrical shapes as shownin FIG. 5. Although the refractive index change is positive (+0.02 to+0.06), these refractive corrective lenses can be made in variouscombinations of convex, plano- or concave to yield a positivecorrection, or negative correction, as shown in FIG. 6. The devices canbe stacked vertically, written separately in different planes, so as toact as a single lens. Additional corrective layers can be written asdesired.

1. A Laser and Optical Configuration for Modifying an Optical Material

A non-limiting embodiment of a laser system 10 for irradiating anoptical, polymeric material with a laser to modify the refractive indexof the material in select regions is illustrated in FIG. 7. A lasersource comprises a Kerr-lens mode-locked Ti:Sapphire laser 12(Kapteyn-Murnane Labs, Boulder, Colo.) pumped by 4 W of afrequency-doubled Nd:YVO₄ laser 14. The laser generates pulses of 300 mWaverage power, 30 fs pulse width and 93 MHz repetition rate atwavelength of 800 nm. Because there is a reflective power loss from themirrors and prisms in the optical path, and in particular, from thepower loss of the objective 20, the measured average laser power at theobjective focus on the material is about 120 mW, which indicates thepulse energy for the femtosecond laser is about 1.3 nJ.

Due to the limited laser pulse energy at the objective focus, the pulsewidth must be preserved so that the pulse peak power is strong enough toexceed the nonlinear absorption threshold of the materials. Because alarge amount of glass inside the focusing objective significantlyincreases the pulse width due to the positive dispersion inside of theglass, an extra-cavity, compensation scheme is used to provide thenegative dispersion that compensates for the positive dispersionintroduced by the focusing objective. Two SF10 prisms 24 and 28 and oneending mirror 32 form a two-pass one-prism-pair configuration. We used a37.5 cm separation distance between the prisms to compensate thedispersion of the microscope objective and other optics within theoptical path.

A collinear autocorrelator 40 using third-order harmonic generation isused to measure the pulse width at the objective focus. Both 2^(nd) and3^(rd) harmonic generation have been used in autocorrelationmeasurements for low NA or high NA objectives. We selected third ordersurface harmonic generation (THG) autocorrelation to characterize thepulse width at the focus of the high-numerical-aperture objectivesbecause of its simplicity, high signal to noise ratio and lack ofmaterial dispersion that second harmonic generation (SHG) crystalsusually introduce. The THG signal is generated at the interface of airand an ordinary cover slip 42 (Corning No. 0211 Zinc Titania glass), andmeasured with a photomultiplier 44 and a lock-in amplifier 46. Afterusing a set of different high-numerical-aperture objectives andcarefully adjusting the separation distance between the two prisms andthe amount of glass inserted, we selected a transform-limited 27-fsduration pulse, which is focused by a 60×0.70 NA Olympus LUCPlanFLNlong-working-distance objective 48.

Because the laser beam will spatially diverge after it comes out of thelaser cavity, a concave mirror pair 50 and 52 is added into the opticalpath in order to adjust the dimension of the laser beam so that thelaser beam can optimally fills the objective aperture. A 3D 100 nmresolution DC servo motor stage 54 (Newport VP-25XA linear stage) and a2D 0.7 nm resolution piezo nanopositioning stage (PI P-622.2CD piezostage) are controlled and programmed by a computer 56 as a scanningplatform to support and locate the samples. The servo stages have a DCservo-motor so they can move smoothly between adjacent steps. An opticalshutter controlled by the computer with 1 ms time resolution isinstalled in the system to precisely control the laser exposure time.With customized computer programs, the optical shutter could be operatedwith the scanning stages to micro-machine different patterns in thematerials with different scanning speed at different position and depthand different laser exposure time. In addition, a CCD camera 58 alongwith a monitor 62 is used beside the objective 20 to monitor the processin real time.

The method and optical apparatus described above can be used to modifythe refractive index of an intraocular lens following the surgicalimplantation of the intraocular lens in a human eye.

Accordingly, the invention is directed to a method comprisingidentifying and measuring the aberrations resulting from the surgicalprocedure. Once the aberrations are identified and quantified usingmethods well known in the art of ophthalmology, this information isprocessed by a computer. Of course, information related to the requisitevision correction for each patient can also be identified anddetermined, and this information can also be processed by a computer.There are a number of commercially available diagnostic systems that areused to measure the aberrations. For example, common wavefront sensorsused today are based on the Schemer disk, the Shack Hartmann wavefrontsensor, the Hartmann screen, and the Fizeau and Twymann-Greeninterferometers. The Shack-Hartmann wavefront measurement system isknown in the art and is described in-part by U.S. Pat. Nos. 5,849,006;6,261,220; 6,271,914 and 6,270,221. Such systems operate by illuminatinga retina of the eye and measuring the reflected wavefront.

Once the aberrations are identified and quantified, the computerprograms determine the position and shape of the optical structures tobe written into the lens material to correct for those aberrations.These computer programs are well known to those of ordinary skill in theart. The computer than communicates with the laser-optical system andselect regions of the lens are irradiated with a focused, visible ornear-IR laser having a pulse energy from 0.05 nJ to 1000 nJ.

2. The Optical, Polymeric Materials

The optical, polymeric materials that can be irradiated by a visible ornear-IR laser according to the methods described in this application canbe any optical, polymeric material known to those of ordinary skill inthe polymeric lens art, particularly those in the art familiar withoptical materials used to make intraocular lenses. The optical,polymeric materials are of sufficient optical clarity, and will have arelatively high refractive index of approximately 1.40 or greater. Manyof these materials are also characterized by a relatively highelongation of approximately 80 percent or greater.

A method of the present invention can be applied to a wide variety ofoptical materials. Non-limiting examples of such materials include thoseused in the manufacture of ophthalmic devices, such as contact lensesand IOLs. For example, the method of the present invention can beapplied to siloxy-containing polymers, acrylic polymers, otherhydrophilic or hydrophobic polymers, copolymers thereof, and mixturesthereof.

Non-limiting example of siloxy-containing polymers that can be used asoptical materials are described in U.S. Pat. Nos. 6,762,271; 6,770,728;6,777,522; 6,849,671; 6,858,218; 6,881,809; 6,908,978; 6,951,914;7,005,494; 7,022,749; 7,033,391; and 7,037,954.

Non-limiting examples of hydrophilic polymers include polymerscomprising units of N-vinylpyrrolidone, 2-hydroxyethyl methacrylate,N,N-dimethylacrylamide, methacrylic acid, poly(ethylene glycolmonomethacrylate), 1,4-butanediol monovinyl ether, 2-aminoethyl vinylether, di(ethylene glycol) monovinyl ether, ethylene glycol butyl vinylether, ethylene glycol monovinyl ether, glycidyl vinyl ether, glycerylvinyl ether, vinyl carbonate, and vinyl carbamate.

Non-limiting examples of hydrophobic polymers include polymerscomprising units of C₁-C₁₀ alkyl methacrylates (e.g., methylmethacrylate, ethyl methacrylate, propyl methacrylate, butylmethacrylate, octyl methacrylate, or 2-ethylhexyl methacrylate;preferably, methyl methacrylate to control mechanical properties),C₁-C₁₀ alkyl acrylates (e.g., methyl acrylate, ethyl acrylate, propylacrylate, or hexyl acrylate; preferably, butyl acrylate to controlmechanical properties), C₆-C₄₀ arylalkyl acrylates (e.g., 2-phenylethylacrylate, benzyl acrylate, 3-phenylpropyl acrylate, 4-phenylbutylacrylate, 5-phenylpentyl acrylate, 8-phenyloctyl acrylate, or2-phenylethoxy acrylate; preferably, 2-phenylethyl acrylate to increaserefractive index), and C₆-C₄₀ arylalkyl methacrylates (e.g.,2-phenylethyl methacrylate, 3-phenylpropyl methacrylate, 4-phenylbutylmethacrylate, 5-phenylpentyl methacrylate, 8-phenyloctyl methacrylate,2-phenoxyethyl methacrylate, 3,3-diphenylpropyl methacrylate,2-(1-naphthylethyl) methacrylate, benzyl methacrylate, or2-(2-naphthylethyl) methacrylate; preferably, 2-phenylethyl methacrylateto increase refractive index).

The method of the invention is particularly suited for modifying therefractive index in select regions of an optical, polymeric siliconehydrogel, or an optical, non-silicone hydrogel. For example, we haveirradiated a silicone hydrogel that can absorb about 36% by weight water(based on the total hydrated weight). The term “hydrogel” refers to anoptical, polymeric material that can absorb greater than 20% by weightwater based on the total hydrated weight.

We have irradiated silicon hydrogel optical materials commercially underthe trade name Balafilcon™. This silicone hydrogel system is based on avinyl carbamate substituted TRIS derivative, that is,tris(trimethylsiloxy)silylpropyl vinylcarbamate) (TPVC). The TPVCmolecule contains the hydrophobic silicone portion and a vinyl carbamategroup. The direct hydrophilic attachment of the carbamate provides thesilicone monomer with sufficient hydrophilic character. Also, the vinylcarbamate group provides a polymerizable vinyl group for the attachmentof hydrophilic monomers. The resulting silicon hydrogels aretransparent, exhibit high Dk and low modulus materials that areinsoluble in water.

We have also irradiated a hydrogel copolymer that comprises about 90%(by weight) N-vinylpyrrolidonc (NVP) and about 10% (by weight)4-t-butyl-2-hydroxycyclohexyl methacrylate. This methacrylate hydrogelcan absorb about 80% (by weight) water because of the high percentage ofNVP. Its refractive index when hydrated is very close to the index ofwater. We have also irradiated HEMA B, which is a poly(2-hydroxyethylmethacrylate) cross-linked with about 0.9% (by weight) of ethyleneglycol dimethacrylate (“EGDMA”). This HEMA-hydrogel can absorb about 37%(by weight) water. Other optical, polymeric materials that can have itsrefractive index modified by irradiating select regions with a laser areprovided as follows.

In one embodiment, the optical polymeric material can be prepared as acopolymer from at least three monomeric components. The first monomericcomponent is present in the copolymer in an amount of at least 70% byweight, and its homopolymer will have a refractive index of at least1.50, preferably at least 1.52 or at least 1.54. The second monomericcomponent is present in the copolymer in an amount from 3% to 20% orfrom 3% to 10%, by weight, and its homopolymer will have a glasstransition temperature of less than about 300° C., preferably less thanabout 220° C. The first and second monomeric components togetherrepresent at least 80% by weight of the copolymer.

The term “homopolymer” refers to a polymer that is derived substantiallycompletely from the respective monomeric component. Minor amounts ofcatalysts, initiators and the like can be included, as is conventionallythe case, in order to facilitate the formation of the homopolymer. Inaddition, the homopolymers of both the first and the second monomericcomponents have sufficiently high molecular weights or degrees ofpolymerization so as to be useful as IOL materials.

Particularly useful first monomeric components include styrene, vinylcarbazole, vinyl naphthalene, benzyl acrylate, phenyl acrylate, naphthylacrylate, pentabromophenyl acrylate, 2-phenoxyethyl acrylate,2-phenoxyethyl methacrylate, 2,3-dibromopropyl acrylate and mixturesthereof. Particularly useful second monomeric components include n-butylacrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, 2-ethoxyethylacrylate, 2,3-dibromopropyl acrylate, n-1, 1-dihydroperfluorobutylacrylate and mixtures thereof.

The third monomeric component is best described as a cross-linkingmonomeric constituent that can form cross-links with the first or thesecond monomeric components. Preferably, the cross-linking monomericcomponent is multi-functional and can chemically react with both thefirst and second monomeric components.

The third component is present in an amount effective to facilitatereturning a deformed IOL made by polymerizing the three monomericcomponents to its original shape in the human eye. The third orcrosslinking monomeric component is often present in a minor amountrelative to the amounts of the first and second monomeric components.Preferably, the third component is present in the copolymer in an amountof less than about 1% by weight of the copolymer. Examples of usefulcrosslinking monomeric components include ethylene glycoldimethacrylate, propylene glycol dimethacrylate, ethylene glycoldiacrylate and the like and mixtures thereof.

The copolymer can further include a fourth component derived from ahydrophilic monomeric component. This fourth component is present in anamount, from 2% to 20% by weight of the copolymer. The fourth componentis preferably present in an amount of less than about 15% by weight ofthe copolymer. Copolymers which include about 15% by weight or more of aconstituent derived from hydrophilic monomeric components tend to formhydrogels if exposed to water.

The term “hydrophilic monomeric component” refers to compounds whichproduce hydrogel-forming homopolymers, that is homopolymers which becomeassociated with at least 20% of water, based on the weight of thehomopolymer, if placed in contact with an aqueous solution. Specificexamples of useful hydrophilic monomeric components include N-vinylpyrrolidone; hydroxyalkyl acrylates and hydroxyalkyl methacrylates, suchas 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropylacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate,4-hydroxybutyl methacrylate, 2,3-dihydroxypropyl acrylate,2,3-dihydroxypropyl methacrylate and the like; acrylamide; N-alkylacrylamides such as N-methyl acrylamide, N-ethyl acrylamide, N-propylacrylamide, N-butyl acrylamide and the like; acrylic acid; methacrylicacid; and the like and mixtures thereof.

The optical, polymeric materials can also be prepared from monomershaving the formula:

wherein: R is H or CH₃; in is 0-10;

Y is nothing, 0, S, or NR wherein R is H, CH₃, C_(n)H_(2n+1) (n=1-10),iso OC₃H₇, phenyl or benzyl;

Ar is any aromatic ring, such as benzene, which can be unsubstituted orsubstituted with H, CH₃, C₂H₅, n-C₃H₇, iso-C₃H₇, OCH₃, C₆H₁₁, Cl, Br,phenyl or benzyl; and

a cross-linking monomer having a plurality of polymerizableethylenically unsaturated groups. The optical material will have a glasstransition temperature not greater than 37° C. and an elongation of atleast 150%.

Exemplary monomers include, but are not limited to: 2-ethylphenoxymethacrylate, 2-ethylphenoxy acrylate, 2-ethylthiophenyl methacrylate,2-ethylthiophenyl acrylate, 2-ethylaminophenyl methacrylate, phenylmethacrylate, benzyl methacrylate, 2-phenylethyl methacrylate,3-phenylpropyl methacrylate, 4-phenylbutyl methacrylate, 4-methylphenylmethacrylate, 4-methylbenzyl methacrylate, 2-2-methylphenylethylmethacrylate, 2-3-methylphenylethyl methacrylate, 2-4-methyl phenylethylmethacrylate, 2-(4-propylphenyl)ethyl methacrylate,2-(4-(1-methylethyl)phenyl)ethyl methacrylate,2-(4-methoxyphenyl)ethylmethacrylate, 2-(4-cyclohexylphenyl)ethylmethacrylate, 2-(2-chlorophenyl)ethyl methacrylate,2-(3-chlorophenyl)ethyl methacrylate, 2-(4-chlorophenyl)ethylmethacrylate, 2-(4-bromophenyl)ethyl methacrylate,2-(3-phenylphenyl)ethyl methacrylate, 2-(4-phenylphenyl)ethylmethacrylate), 2-(4-benzylphenyl)ethyl methacrylate, and the like,including the corresponding methacrylates and acrylates.

The copolymerizable cross-linking agent can be any terminallyethylenically unsaturated compound having more than one unsaturatedgroup. Suitable cross-linking agents include, for example: ethyleneglycol dimethacrylate, diethylene glycol dimethacrylate, allylmethacrylate, 1,3-propanedioldimethacrylate, allylmethacrylate1,6-hexanediol dimethacrylate, 1,4-butanediol dimethacrylate, and thelike. A preferred cross-linking agent is 1,4-butanediol diacrylate.

The aryl acrylate/methacrylate based optical materials will generallycomprise a greater mole percent of acrylate ester residues than ofmethacrylate ester residues. It is preferred that the aryl acrylatemonomers constitute from about 60 mole percent to about 95 mole percentof the polymer, while the aryl methacrylate monomers constitute fromabout 5 mole percent to about 40 mole percent of the polymer. Mostpreferred is a polymer comprising about 60-70 mole percent 2-phenylethylacrylate and about 30-40 mole percent 2-phenylethyl methacrylate.

The optical, polymeric materials can also be prepared from a reinforcedcross-linked silicone elastomer which includes a polymer containing 12to 18 mol percent of aryl substituted siloxane units of the formulaR⁴R⁵—SiO. In the formula, R⁴ and R⁵ are the same or different andrepresent phenyl, mono-lower alkyl substituted phenyl groups, ordi-lower alkyl substituted phenyl groups. Preferably both R⁴ and R⁵ arephenyl.

The polymer has end blockers containing siloxane units of the formulaR¹R²R³—SiO₅ wherein R¹ and R² are alkyl, aryl or substituted alkyl orsubstituted aryl groups, and R¹ and R² can be the same or different. TheR³ group of the end blocking siloxane units is an alkenyl group.Preferably, the end blacker is a dimethylvinyl siloxane unit.

The balance of the polymer consists of dialkyl siloxane units of theformula R⁶R⁷—SiO wherein R⁶ and R⁷ are the same or different from andare methyl or ethyl groups, and the polymer has a degree ofpolymerization from 100 to 2000. Preferably, R⁶ and R⁷ are both methyl,and the degree of polymerization is approximately 250.

A trimethyl silyl treated silica reinforcer is finely dispersed in thepolymer, in a weight ratio of approximately 15 to 45 parts of thereinforcer to 100 parts of the polymer. Preferably, there isapproximately 27 parts of reinforcer to 100 parts of the copolymer.

The optical, polymeric material can also be prepared by polymerizing thefollowing monomeric components: (A) 5-25% by weight of acrylaterepresented by the general formula

wherein Ar represents an aromatic ring of which hydrogen atom may besubstituted by a substitutional group, X represents an oxygen atom or adirect bonding, and m represents an integer of 1 to 5; (B) 50 to 90% byweight of 2-hydroxyethyl (meth)acrylate; and (C) 5 to 45% by weight of a(meth)acrylate monomer though not of the formula that represent monomer(A) and not 2-hydroxyethyl (meth)acrylate. Also, the coefficient ofwater absorption of the homopolymer of monomer (C) is not more than 30%by weight.

In the present invention the coefficient of water absorption is definedas the following equation: water absorption (% wt)=(W−W_(o))/W_(o)×100

wherein the value is calculated at 25° C. by using the specimen having 1mm thickness at cutting, W represents a weight of the specimen inequilibrium state of water, and W_(o) represents a weight of thespecimen in a dry state.

An exemplary listing of (meth)acrylate monomer (C) include an alkyl(meth)acrylate containing a straight chain, a branched chain or cyclicchain such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl(meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexylmeth)acrylate, heptyl (meth)acrylate, nonyl (meth)acrylate, stearylmeth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, lauryl(meth)acrylate, pentadecyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,cyclopentyl (meth)acrylate, (meth)acrylate, cyclohexyl (meth)acrylate:an alkyl (meth)acrylate containing 1 to 5 carbon atoms of alkyl group: ahydroxyalkyl (meth)acrylate containing a straight chain, a branchedchain or cyclic chain, except for 2-HE(M)A (B), and any mixture thereof.Among the alkyl methacrylates those containing 1 to 3 carbon atoms ofalkyl group are preferred. Among the hydroxyalkyl methacrylates thosecontaining 3 to 6 carbon atoms of hydroxyalkyl group are preferred.

The optical, polymeric material can also be prepared by copolymerizing aspecific monomer mixture comprising perfluorooctylethyloxypropylene(meth)acrylate, 2-phenylethyl (meth)acrylate, an alkyl (meth)acrylatemonomer having the following general formula,

wherein R is hydrogen or methyl and R¹ is a linear or branched C₄-C₁₂alkyl group, and a crosslinking monomer. An examplary list of alkyl(meth)acrylate monomer include n-butyl acrylate, isobutyl acrylate,isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate,isooctyl acrylate, decyl acrylate, isodecyl acrylate, and the like.

The perfluorooctylethyloxypropylene (meth)acrylate is present from 5% to20% by weight, the 2-phenylethyl (meth)acrylate is present from 40% to60% by weight, the alkyl (meth)acrylate monomer is present from 30% to50% by weight and the crosslinking agent is present from 0.5% to 4% byweight.

The optical, polymeric material can also be prepared from a first(meth)acrylate monomer, a second aromatic monomer, and a third, highwater content hydrogel-forming monomer. The first monomeric component ispresent from 30% to 50% by weight, the second monomeric component ispresent from 10% to 30% by weight, and the third monomeric component ispresent from 20% to 40% by weight. A crosslinking agent is also used toprepare the material.

The first monomeric component is an aryl acrylate or an arylmethacrylate, and are commonly referred to as aryl (meth)acrylatemonomers. The term “aryl” implies that the compound contains at leastone aromatic group. Exemplary aryl (meth)acrylate monomers includeethylene glycol phenyl ether acrylate (EGPEA), poly(ethylene glycolphenyl ether acrylate) (polyEGPEA), phenyl methacrylate, 2-ethylphenoxymethacrylate, 2-ethylphenoxy acrylate, hexylphenoxy methacrylate,hexylphenoxy acrylate, benzyl methacrylate, 2-phenylethyl methacrylate,4-methylphenyl methacrylate, 4-methylbenzyl methacrylate,2-2-methylphenylethyl methacrylate, 2-3-methylphenylethyl methacrylate,2-4-methylphenylethyl methacrylate, 2-(4-propylphenyl)ethylmethacrylate, 2-(4-(1-methylethyl)phenyl)ethyl methacrylate,2-(4-methoxyphenyl)ethylmethacrylate, 2-(4-cyclohexylphenyl)ethylmethacrylate, 2-(2-chlorophenyl)ethyl methacrylate,2-(3-chlorophenyl)ethyl methacrylate, 2-(4-chlorophenyl)ethylmethacrylate, 2-(4-bromophenyl)ethyl methacrylate,2-(3-phenylphenyl)ethyl methacrylate, 2-(4-phenylphenyl)ethylmethacrylate), 2-(4-benzylphenyl)ethyl methacrylate, and the like,including the corresponding methacrylates and acrylates, and includingmixtures thereof. EGPEA and polyEGPEA are two of the more preferredfirst monomeric components.

The second monomeric component includes a monomer having an aromaticring with a substituent having at least one site of ethylenicunsaturation. Preferably, this second monomeric component is not anacrylate. Such monomers have the general formula:

wherein X is H or CH₃, and Ar is a substituted or unsubstituted aromaticring. Representative second monomeric components include, for example,substituted and unsubstituted styrene compounds. These compounds may besubstituted with hydrogen, halogen (e.g. Br, Cl, F), lower alkyl groups(e.g. methyl, ethyl, propyl, butyl, isopropyl), and/or lower alkoxygroups. Suitable aromatic monomers include, for example: styrene,methoxy styrene, and chlorostyrene.

The third monomeric component comprises a high water contenthydrogel-forming monomer. Preferably, the third monomeric componentincludes a methacrylate without an aromatic substituent. Suitable highwater content hydrogel-forming monomers include, for example:hydroxyethyl methacrylate (HEMA), hydroxyethoxyethyl methacrylate(HEEMA), hydroxydiethoxyethyl methacrylate, methoxyethyl methacrylate,methoxyethoxyethyl methacrylate, methoxydiethoxyethyl methacrylate,ethylene glycol dimethacrylate, n-vinyl-2-pyrrolidone, methacrylic acid,vinyl acetate and the like and mixtures thereof. One skilled in this artwill recognize that many other high water content hydrogel-formingmonomers are likely to be operable in view of this disclosure. HEMA andHEEMA are two of the more preferred third monomeric components.

The copolymer may also include a crosslinking agent. The copolymerizablecrosslinking agent(s) useful in forming the copolymeric material of theinvention include any terminally ethylenically unsaturated compoundhaving more than one unsaturated group. Preferably, the crosslinkingagent includes a diacrylate or a dimethacrylate. The crosslinking agentmay also include compounds having at least two (meth)acrylate and/orvinyl groups. Particularly preferred crosslinking agents includediacrylate compounds

The optical, polymeric materials are prepared by generally conventionalpolymerization methods from the respective monomeric components. Apolymerization mixture of the monomers in the selected amounts isprepared and a conventional thermal free-radical initiator is added. Themixture is introduced into a mold of suitable shape to form the opticalmaterial and the polymerization initiated by gentle heating. Typicalthermal, free radical initiators include peroxides, such as benzophenoneperoxide, peroxycarbonates, such as bis-(4-t-butylcyclohexyl)peroxydicarbonate, azonitriles, such as azobisisobytyronitrile, and thelike. A preferred initiator is bis-(4-t-butylcyclohexyl)peroxydicarbonate (PERK). Alternatively, the monomers can bephotopolymerized by using a mold which is transparent to actinicradiation of a wavelength capable of initiating polymerization of theseacrylic monomers by itself. Conventional photoinitiator compounds, e.g.,a benzophenone-type photoinitiator, can also be introduced to facilitatethe polymerization.

EXAMPLES Example 1. Forming Structures in Optical Polymeric Materials

The optical system described was used to form line structures in selectregions of optical materials. Experiments were conducted with threepolymeric materials (Bausch & Lomb Incorporated, Rochester, N.Y.):PV2526-164, RD1817, and HEMA B. PV2526-164 is a silicone-containinghydrogel that can absorb about 36% (by total weight). RD1817 is ahydrogel copolymer that comprises about 90% (by weight)N-vinylpyrrolidone (“NVP”) and about 10% (by weight)4-t-butyl-2-hydroxycyclohexyl methacrylate and that can absorb about 80%(by weight) water. Its refractive index when hydrated is very close tothe index of water. HEMA B is poly(2-hydroxyethyl methacrylate)cross-linked with about 0.9% (by weight) of ethylene glycoldimethacrylate (“EGDMA”), also a hydrogel, which can absorb about 37%(by weight) water. The refractive indices of PV2526-164, RD1817, andHEMA B are 1.422, 1.363, and 1.438, respectively, when they are in thehydrated state. Each of the hydrogel samples was maintained in asolution (Bausch and Lomb “Renu” solution) between a microscope slideand a glass cover slip to maintain their water-content duringmicro-machining and subsequent optical measurements. The thickness ofthese hydrogel samples in the solution is about 700 μm. The hydratedsample was mounted horizontally on the scanning platform, and thefemtosecond laser beam was directed vertically downward through thehigh-numerical-aperture objective and was focused inside the bulkmaterial, as shown in Figure B, at a depth of about 100 μm from theupper surface of the sample. Periodic gratings structures were createdwith a scanning speed of 0.4 μm/sec in an X-Y plane perpendicular to thelaser beam. An Olympus BX51 Model microscope was used to observe thegratings that were created inside these three materials.

The microscope images showed periodically parallel gratings inside thesamples with 5-μm spacing. The gratings were difficult to see inbright-field microscope, indicating that these gratings exhibit lowscattering. The width of the gratings was about 1 μm, which wassignificantly smaller than the laser focus diameter of 2.5 μm that wasmeasured using a knife-edge method. Therefore, the modified region isstill within the laser irradiation focus volume although there would beheat accumulation generated in the process.

A cross section of the PV2526-164 sample revealed that the cross sectionof the gratings was elliptical with the longer axis oriented in thedirection of the laser beam, indicating that there was a larger laserintensity distribution in this direction. By carefully adjusting thecover-slip correction of the objective, this spherical aberration couldbe minimized.

These gratings were investigated by focusing an unpolarized He—Ne laserbeam with a wavelength of 632.8 nm on these gratings and monitoring thediffraction pattern. The diffraction angles showed good agreement withthe diffraction equationmλ=d sin θ  (1)

where m is the diffraction order, λ is the wavelength of the incidentlaser beam which here is 632.8 nm, and d is the grating period.

The diffraction efficiency of the grating can be measured, and since theefficiency is a function of the refractive index change, it may be usedto calculate the refractive index change in the laser irradiationregion. Consider the grating as a phase grating, its transmittancefunction could be written as

$\begin{matrix}{{t\left( {x_{0},y_{0}} \right)} = {{{\left( {e^{i\;\phi_{2}} - e^{i\;\phi_{1}}} \right){{rect}\left( \frac{x_{0}}{a} \right)}} \star {\frac{1}{d}{{comb}\left( \frac{x_{0}}{d} \right)}}} + e^{i\;\phi_{1}}}} & (2)\end{matrix}$where a is the grating line width, d is the groove spacing, ϕ₂ and ϕ₁are the phase delays through the lines and ambient region respectively,

${\phi_{2} = {{2\pi \times \frac{\left( {n + {\Delta\; n}} \right) \times b}{\lambda}\mspace{14mu}{and}\mspace{14mu}\phi_{1}} = {2\;\pi \times \frac{n \times b}{\lambda}}}},$b is the thickness of the grating line, n is the average refractiveindex of the material, Δn is the average refractive index change in thegrating lines, and λ is the incident light wavelength of the measurement(632.8 nm). Here, the grating line width is 1 μm and the thickness is 3μm. The index change within the laser effect region can be approximatedto be uniform. The convolution theorem can be used to calculate thespectrum of the grating such asT(f _(x) ,f _(y))=F{t(x ₀ ,y ₀)}=(e ^(iϕ) ¹ −e ^(iϕ) ² )a sin c(af_(x))comb(df _(x))δ(f _(y))+e ^(iϕ) ¹ δ(f _(x) ,f _(y))  (3)

Then, the intensity distribution of the grating diffraction pattern is:

$\begin{matrix}{{I\left( {x,y} \right)} = {\left( \frac{1}{\lambda\; z} \right)^{2} \times \left\lbrack {{\left( {e^{i\;\phi_{2}} - e^{i\;\phi_{1}}} \right)\frac{a}{d}{\sum\limits_{n = {- \infty}}^{\infty}{\sin\mspace{14mu} c\mspace{11mu}\left( \frac{an}{d} \right)\mspace{11mu}\delta\mspace{11mu}\left( {{\frac{x}{\lambda\; z} - \frac{n}{d}},\frac{y}{\lambda\; z}} \right)}}} + {e^{i\;\phi_{1}}{\delta\left( {\frac{x}{\lambda\; z},\frac{y}{\lambda\; z}} \right)}}} \right\rbrack^{2}}} & (4)\end{matrix}$

From this formula, the intensity of the 0^(th) (I₀), 1^(st) (I₁), and2^(nd) (I₂) order diffraction light is

$\begin{matrix}{I_{0} = {\left( \frac{1}{\lambda\; z} \right)^{2} \times \left\lbrack {{\left( {e^{i\; 2\;\pi \times \frac{{({n + {\Delta\; n}})} \times b}{\lambda}} - e^{i\; 2\pi \times \frac{n \times b}{\lambda}}} \right)\frac{a}{d}} + e^{i\; 2\;\pi \times \frac{n \times b}{\lambda}}} \right\rbrack^{2}}} & (5) \\{I_{1} = {\left( \frac{1}{\lambda\; z} \right)^{2} \times \left\lbrack {\left( {e^{i\; 2\;\pi \times \frac{{({n + {\Delta\; n}})} \times b}{\lambda}} - e^{i\; 2\pi \times \frac{n \times b}{\lambda}}} \right)\frac{a}{d}\sin\mspace{14mu}{c\left( \frac{a}{d} \right)}} \right\rbrack^{2}}} & (6) \\{and} & \; \\{I_{2} = {\left( \frac{1}{\lambda\; z} \right)^{2} \times \left\lbrack {\left( {e^{i\; 2\;\pi \times \frac{{({n + {\Delta\; n}})} \times b}{\lambda}} - e^{i\; 2\pi \times \frac{n \times b}{\lambda}}} \right)\frac{a}{d}\sin\mspace{14mu}{c\left( \frac{2a}{d} \right)}} \right\rbrack^{2}}} & (7)\end{matrix}$

By comparing the light intensities of 1^(st), 2^(nd) and 0^(th)diffraction orders, the refractive index change within the grating linescan be determined. FIG. 3 shows the ratio of intensity of the 1^(st) and2^(nd) diffraction order to 0^(th) order of the grating in PV2526-164 is0.1374 and 0.0842 respectively, and the corresponding refractive indexchange determined by the analysis is about 0.06. Using the same method,we determined the average refractive index change in RD1817 and HEMA Bto be 0.05±0.0005 and 0.03±0.0005. Thus, it was demonstrated that therefractive index of a material can be modified by applying an ultrafastlaser thereto.

We used Raman spectroscopy to provide information on the structural ormolecular changes that occur in the irradiated regions on the optical,polymeric materials. In the Raman scattering experiments, the hydrogelpolymer samples are placed in a confocal micro-Raman spectrometerequipped with an X-Y scan stage with nanometer resolution. A 632.8 nmHe—Ne laser is focused on the surface of the material in order to obtainthe Raman scattering signal. Due to the difference between therefractive indices of the bulk and the irradiated regions, the scatteredlight at the interface was monitored in order to ensure the laser focuswas located into the irradiated region. FIGS. 9A and 9B show the Ramanspectra of the base material and the irradiated region (micromachinedfeature) of the hydrogel, respectively. The main Raman peaks arecentered at 2890 cm⁻¹ and 2958 cm⁻¹ (—CH_(x) bond stretching), 1422 cm⁻¹(—CH_(x) bond deformation), 930 cm⁻¹ (C—C bond skeletal), 800 cm⁻¹(—Si—O—Si— bond stretching), 686 cm⁻¹ to 752 cm⁻¹ (—Si—(CH₃)_(x) bondstretching) and 638 cm⁻¹ (—Si—O₃ bond stretching) [4]. Comparing the twospectra strongly suggests there is no significant structural or chemicalchange between the irradiated regions and the base material.

The above Raman results are surprising in light of recent Raman spectraanalysis of fused silica modified by femtosecond laser pulses. See, J.W. Chan, T. Huser, S. Risbud, D. M. Krol, in “Structural changes infused silica after exposure to focused femtosecond laser pulses,” Opt.Lett. 26, 1726-1728 (2001). The results of our Raman experiments,however, may explain why we do not observe any light scattering by theirradiated regions (micromachined structures) in the optical materials.Our Raman spectra also suggest that low-pulse-energy femtosecondirradiation of optical, polymeric materials do not cause strongstructural changes in the materials, even when the change of therefractive index is much higher than that obtained for fused silica.

FIG. 10 shows the Raman spectrum of a damage spot in balafilcon A, ifhigher energy femtosecond pulses are used in the irradiation(micromachining) process. Only Raman bands related to disordered carbonare detected (D band at ˜1330 cm⁻¹ and G band at ˜1600 cm⁻¹) indicatingthat the chemical bonds forming the hydrogel structure are broken.

We also irradiated an acrylic material comprising about 80 wt % HEMA and20 wt % MMA with a water content of about 26% using similar processconditions described above. Such a material is representative of Bausch& Lombs intraocular lens sold under the tradename Akreos®. FIG. 11 showsa radial pattern micromachined into the acrylic material. FIG. 11 is apictorial representation of the optical material with non-irradiatedregions 120 and irradiated (micromachined) regions 124.

We also irradiated a silicone hydrogel material using similar processconditions described above. Such a material is representative of Bausch& Lombs intraocular lens marketed under the tradename SoFlex®SE. Asimilar radial pattern as shown in FIG. 11 was micromachined into thesilicone material.

Although the foregoing Examples describes a creation of grating lines,cylinders and radial patterns in optical materials, other features alsocan be created using a method of the present invention. For examples,arrays of dots (e.g., having a dimension in the nanometer range) can becreated by directing the laser beam at discrete points or spots withinthe material. Such an array can be arranged substantially on one planeor several such arrays can be created at different depths within thematerial. A material thus modified can be advantageously useful whenlight is not substantially scattered by the dots.

While specific embodiments of the present invention have been describedin the foregoing, it will be appreciated by those skilled in the artthat many equivalents, modifications, substitutions, and variations maybe made thereto without departing from the spirit and scope of theinvention as defined in the appended claims.

We claim:
 1. A method of changing the index of refraction of an optical,polymeric material, the method comprising: irradiating selected regionsof the optical, polymeric material with laser light from a visible ornear-IR laser focused through a focusing objective, having a pulseenergy from 0.05 nJ to 1000 nJ and a light wavelength from 400 nm to1200 nm; and scanning a focus of the laser light through the selectedregions for producing a change in refractive index of the optical,polymeric material, thereby forming a three-dimensional refractivestructure that exhibits little or no scattering loss; wherein the lasersystem includes negative compensation to compensate for a positivedispersion of pulse width of the laser introduced by at least one of thefocusing objective and other optical elements within an optical path ofthe laser.
 2. The method of claim 1 wherein the focus of the laser lightis moved in an X-Y plane perpendicular to the laser beam.
 3. The methodof claim 2 wherein the three-dimensional refractive structure is definedby a series of line scans, the line scans having a width from 0.2 μm to3 μm, and a height from 0.4 μm to 8 μm, wherein the height is measuredin a Z-direction parallel to the laser beam.
 4. The method of claim 2wherein the three-dimensional refractive structure is a verticallystacked structure wherein the irradiated regions are formed separatelyin different planes in the optical, polymeric material in a Z-directionparallel to the laser beam.
 5. The method of claim 1 wherein the laserlight has a pulse energy from 0.2 nJ to 10 nJ.
 6. The method of claim 1wherein the optical device is selected from a contact lens, anintraocular lens, a corneal inlay, a corneal ring or a keratoprosthesis.7. The method of claim 1, wherein the visible or near-IR laser generatespulses having a pulse width of 4 fs to 100 fs.
 8. The method of claim 1in which the step of scanning includes continuously scanning the laserlight over the selected regions of the optical, polymeric material toform the three-dimensional refractive structure as a volume filledstructure.
 9. The method of claim 8 in which the volume filled structureis a three-dimensionally shaped lens.
 10. The method of claim 9 in whichthe three-dimensionally shaped lens is a converging lens.
 11. The methodof claim 9 in which the three-dimensionally shaped lens is a diverginglens.
 12. The method of claim 9 in which the three-dimensionally shapedlens is a cylindrical lens.
 13. A method of changing the index ofrefraction of an optical, polymeric material, the method comprising:irradiating selected regions of the optical, polymeric material withlaser light from focused, visible or near-IR laser having a pulse energyfrom 0.05 nJ to 1000 nJ and a light wavelength from 400 nm to 1200 nm;and scanning a focus of the laser light through the selected regions forproducing a change in refractive index of the optical, polymericmaterial, thereby forming a three-dimensional refractive structure thatexhibits little or no scattering loss; in which the optical, polymericmaterial is in the form of an optical device and the three-dimensionalrefractive structure corrects for measured aberrations in the opticaldevice.
 14. The method of claim 13 including a step of measuring aposition and shape of the three-dimensional refractive structure tocorrect for the measured aberrations in the optical device.
 15. Themethod of claim 13, wherein the laser light is focused through afocusing objective, and wherein the laser system includes negativecompensation to compensate for a positive dispersion of pulse width ofthe laser introduced by at least one of the focusing objective and otheroptical elements within an optical path of the laser.
 16. A method ofchanging the index of refraction of an optical, polymeric material, themethod comprising: irradiating selected regions of the optical,polymeric material with laser light from focused, visible or near-IRlaser having a pulse energy from 0.05 nJ to 1000 nJ and a lightwavelength from 400 nm to 1200 nm; and scanning a focus of the laserlight through the selected regions for producing a change in refractiveindex of the optical, polymeric material, thereby forming athree-dimensional refractive structure that exhibits little or noscattering loss; wherein the optical, polymeric material is a hydrated,optical, polymeric material.
 17. The method of claim 16, wherein thelaser light is focused through a focusing objective, and wherein thelaser system includes negative compensation to compensate for a positivedispersion of pulse width of the laser introduced by at least one of thefocusing objective and other optical elements within an optical path ofthe laser.